Typically, relatively large and heavy wires such as aluminum wire are used in wedge wire bonding for high power electronic packages, which conduct larger currents in operation. A wedge wire bonding machine that is configured to bond such wires generally comprises a bond head that is able to position itself relative to the electronic packages in the X, Y, Z and theta axes for wedge wire bonding. Having a theta axis is necessary in wedge wire bonding for aligning an orientation of a wire bond with the wire being fed between a first bond and a second bond.
Heavy wire may commonly be produced in multiple forms, for example, they may have round cross-sections (hereinafter referred to as “round wires”) or ribbon-shaped rectangular cross-sections (hereinafter referred to as “ribbon wires”). Conventionally, a bond head of the wire bonder is adapted to bond only one type of wire, such as either round wire or ribbon wire. Thus, when the bond head is adapted to bond round wire, the bond head module needs to be replaced to configure the wire bonding machine for bonding ribbon wire, as explained below.
In a typical heavy aluminum wire bonder, there are three major components at the vicinity of the bonding tip in order to perform wire bonding: a wire clamp module, a vibration-generating transducer with a wedge, and a cutter module. The transducer generates ultrasonic power and induces ultrasonic vibrations of the wedge to bond the wire to a surface of a substrate using heat and ultrasonic energy. The aluminum wire is guided and held by the wire clamp module. When the transducer is triggered, the ultrasonic vibrations of the wedge will transmit to the wire underneath the wedge tip and perform bonding between the wire and the surface of the substrate. After the bonding process, the bonded wire is separated from the bonding tip by the cutter module.
To achieve a good bond, the wire should be well captured under the wedge tip. Good bonding can only be achieved when the bonding wire can be firmly guided to the wedge tip. This is highly dependent on the design and the alignment of the wire clamp which is designed for guiding and holding the bonding wire to the wedge tip. Proper setup of wire clamp is thus needed to achieve good bonding quality.
The heavy wire bonder usually has the capability to bond ribbon wire in addition to round wire as they are compatible and have similar process characteristics. On the other hand, in order to bond ribbon wire, the bond head module needs to be exchanged. The necessity of exchanging the bond head module is due to the different orientations of the respective bonding wires. Lateral placement accuracy is more important for bonding round wire, while placement accuracy of the ribbon wire along the transducer axis is more important for bonding ribbon wire. Consequently, the arrangements of the wire clamps for bonding the different types of wires are different.
FIG. 1 is a schematic configuration of a conventional bond head 100 of a wedge wire bonder used for bonding round wire 102, whereas FIG. 2 is a schematic configuration of a conventional bond head 101 of a wedge wire bonder used for bonding ribbon wire 104. They demonstrate the differences between the conventional round wire bond head 100 and the conventional ribbon bond head 101 respectively.
The schematic figures show the three major components of a bonding tip: a cutter 106, a wedge 108 attached to a transducer and a wire clamp having clamping plates 110. The order and relationship between the three components may vary depending on the applications and designs. The clamping plates 110 of the wire clamp in a conventional round wire bond head 100 will be arranged parallel to a transducer axis 112 as the wire clamp plates function as lateral guides for the round wire 102 in addition to their clamping function.
However, due to the characteristics and generally rectangular cross-section of ribbon wires 104, the design of the clamping plates 110 for round wires cannot conventionally be used for ribbon wire 104. The clamping plates 110 need to clamp onto a wider surface of the ribbon wire 104, or else the wire may be damaged. The clamping plates 110 also guide the position of the ribbon wire 104 with respect to the wedge 108. Thus, it is necessary for the wire clamping plates 110 of the wire clamp to be always perpendicular to the transducer axis 112.
Due to the differences between design requirements of the clamping plates 110, the bond head 100 for bonding round wire 102 and the bond head 101 for bonding ribbon wire 104 are different. Hence, to convert the wire bonding machine between bonding round wire 102 and ribbon wire 104, the whole bond head 100, 101 module of the wire bonding machine needs to be changed.
The requirement of having to replace the bond head in order to bond different types of wire is disadvantageous in that it is time-consuming to install the new bond head. Furthermore, the bonding tool will have to be adjusted and calibrated in order to start using the new bond head.